Embodiments of the present disclosure relate to fuel vapor processing apparatus used mainly for vehicles such as automobiles having internal combustion engines mounted thereto.
Known fuel vapor processing apparatuses include a first canister having therein an adsorbent capable of adsorbing fuel vapor generated in a fuel tank of a vehicle and allowing desorption of the adsorbed fuel vapor, and a second canister having therein an adsorbent capable of adsorbing fuel vapor contained in a breakthrough gas discharged from the first canister and allowing desorption of the adsorbed fuel vapor (see, for example, US2011/0214572A1). In the apparatus disclosed in US2011/0214572A1, a partition member allowing passage of gas is arranged inside the second canister, whereby the interior of the second canister is divided into inner and outer passages communicating with each other. The outer passage is used as an adsorption passage in which the adsorbent is arranged, and the inner passage is used an air passage through which air flows. As is known in the art, in a canister using an adsorbent such as activated carbon, when fuel vapor is adsorbed, the adsorption performance of the adsorbent may deteriorate as the temperature of the adsorbent increases due to an exothermic reaction. Conversely, when the adsorbed fuel component is desorbed, the desorption efficiency (i.e., purge performance) of the adsorbent may deteriorate as the temperature of the adsorbent decreases due to an endothermic reaction.
In the known fuel vapor processing apparatus, air (e.g., hot air) heated by adsorption heat generated by the adsorbent of the first canister may pass through the air passage of the second canister during refueling. As a result, the adsorbent in the adsorption passage may be heated. However, the circumference of the adsorption passage is exposed to the outside, so that the heat of the adsorption passage may be dissipated to the outside. Thus, the desorption efficiency of the adsorbent may deteriorate for the next purge operation. This may result in an increase in the residual amount of the fuel component (HC) per pore of the adsorbent of the second canister, resulting in an increase in the blow-through quantity of the fuel component.
Therefore, there has been a need in the art for suppressing dissipation to the outside of the heat in the adsorption passage of the second canister.